Charging system and charger

ABSTRACT

A charger that charges a battery unit including a secondary battery, includes a receiving unit, a detection unit, a determination unit, and a control unit. The receiving unit receives, from the battery unit, battery state information indicating a state of the battery unit, if the secondary battery is being charged. The detection unit detects charge state information indicating the state of the battery unit, if the secondary battery is being charged. The determination unit determines, using the battery state information and the charge state information, whether the battery unit is in a normal state. The control unit controls charging of the secondary battery in the battery unit depending on whether the battery unit is in the normal state.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a charger and a charging systemincluding the charger.

2. Description of the Related Art

In a method of charging a secondary battery such as a lithium-ionbattery, a charger measures a charging voltage, a charging current, anda partial voltage of a battery pack, and controls charging of thebattery pack. Japanese Patent Application Laid-Open No. 10-201109discusses a charging system that a charger can be communicated with abattery pack and controls charging.

In the foregoing example of the related art, the charger controlscharging depending on information of the battery pack which is receivedfrom the battery pack. However, the charger of the related art isincapable of determining, using the information of the battery packwhich is received from the battery pack, whether an error has occurredin the battery pack.

SUMMARY OF THE INVENTION

The present invention is directed to a charger and a charging system fordetermining, using information of the battery pack which is receivedfrom the battery pack, whether a battery pack is in a normal state. Thepresent invention is directed to a charger and a charging system forsafely controlling an operation of charging a battery pack.

According to an aspect of the present invention, a charger that chargesa battery unit including a secondary battery, includes a receiving unitthat receives, from the battery unit, battery state informationindicating a state of the battery unit, if the secondary battery isbeing charged; a detection unit that detects charge state informationindicating the state of the battery unit, if the secondary battery isbeing charged; a determination unit that determines, using the batterystate information and the charge state information, whether the batteryunit is in a normal state; and a control unit that controls charging ofthe secondary battery in the battery unit depending on whether thebattery unit is in the normal state.

According to an aspect of the present invention, a charging systemincludes a battery unit including a secondary battery; and a chargerthat charges the secondary battery. The battery unit includes a firstdetection unit that detects battery state information indicating a stateof the battery unit, if the secondary battery is being charged; and asending unit that sends the battery state information to the charger.The charger includes: a second detection unit that detects charge stateinformation indicating a state of the battery unit, if the secondarybattery is being charged; a receiving unit that receives the batterystate information from the battery unit, if the secondary battery isbeing charged; a determination unit that determines, using the batterystate information and the charge state information, whether the batteryunit is in a normal state; and a control unit that controls charging ofthe secondary battery in the battery unit depending on the battery unitis in the normal state.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the present invention and, together with the description,serve to explain the principles of the present invention.

FIG. 1 is a block diagram showing an exemplary configuration of acharger and a battery pack according to a first embodiment of thepresent invention.

FIG. 2 is a flowchart describing an operation of charging, with the useof the charger, the battery pack attached to the charger.

FIG. 3 is a flowchart describing a measurement value checking operationof the charger according to the first embodiment.

FIG. 4 is a flowchart describing a measurement value checking operationof the charger according to a second embodiment.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the presentinvention will now be described in detail below with reference to theattached drawings.

First Embodiment

FIG. 1 is a block diagram showing an exemplary configuration of acharging system according to a first embodiment of the presentinvention. The charging system shown in FIG. 1 includes a charger 200and a battery pack 100. The charger 200 can charge the battery pack 100attached to the charger 200.

The battery pack 100 includes a battery cell 101, a batterymicrocomputer 102, a temperature detector 103, a current detector 104, avoltage detector 105, a communication unit 106, and a control unit 107.The battery cell 101 is a secondary battery such as a lithium-ion cellor a nickel-hydride cell. The battery microcomputer 102 is located inthe battery pack 100 and includes the current detector 104, the voltagedetector 105, the communication unit 106, and the control unit 107.

The temperature detector 103 is implemented by a temperature detectingdevice such as a thermistor and can calculate a resistance value of thetemperature detecting device using a reference voltage. The temperaturedetector 103 can use a first measurement method of calculating theresistance value of the temperature detecting device using a referencevoltage supplied from the battery microcomputer 102, and a secondmeasurement method of calculating the resistance value of thetemperature detecting device using a reference voltage supplied from acharging control integrated circuit (IC) 203. The temperature of thebattery pack 100 can be calculated from the resistance value calculatedusing the first measurement method. The temperature of the battery pack100 can be calculated from the resistance value calculated using thesecond measurement method.

The current detector 104 detects a charging current flowing through thebattery cell 101 using the voltage of a current detecting resistor. Thevoltage detector 105 detects the voltage of the battery cell 101. Thecontrol unit 107 controls the current detector 104, the voltage detector105, and the communication unit 106 and can calculate the temperature ofthe battery pack 100 from the resistance value calculated using thefirst measurement method.

The control unit 107 outputs battery state information to thecommunication unit 106. In the present embodiment, the charging currentvalue detected by the current detector 104, the charging voltage valuedetected by the voltage detector 105, the temperature of the batterypack 100 calculated by the control unit 107, and the charge capacity ofthe battery cell 101 calculated by the control unit 107 are called“battery state information”. The control unit 107 integrates thecharging current flowing through the battery cell 101, which is detectedby the current detector 104, thereby calculating the charge capacity ofthe battery cell 101. The communication unit 106 sends the battery stateinformation output from the control unit 107 to the charger 200.

The charger 200 includes an alternating current (AC) input unit 201, analternating current-to-direct current (AC/DC) converter 202, thecharging control IC 203, a current control device 204, a currentdetecting device 205, a display unit 206, and a charger microcomputer301. The battery microcomputer 301 is located in the charger 200 andincludes a current detector 302, a voltage detector 303, a communicationunit 304, and a control unit 305. The AC input unit 201 is connected toa commercial AC power supply and supplies power to the charger 200. TheAC/DC converter 202 rectifies power supplied from the commercial ACpower supply and converts the rectified power into a DC voltage that iseasy to use.

The charging control IC 203 controls the charging current flowingthrough the battery pack 100. The current control device 204 is a devicethat restricts the charging current, such as a transistor that restrictsthe charging current or a diode that prevents backflow. The currentdetecting device 205 is, for example, a resistor that detects thecharging current. The display unit 206 is a display device such as alight-emitting diode (LED) or a liquid crystal display (LCD) and informsthe user of the charge state of the charger 200. The current detector302 detects the charging current value from the value detected by thecurrent detecting device 205. The voltage detector 303 detects the valueof a charge voltage applied to a terminal of the battery pack 100. If nocharge voltage is being applied, the voltage detector 303 can detect theterminal voltage of the battery pack 100 attached to the charger 200.

The control unit 305 controls charging of the battery pack 100 attachedto the charger 200. The control unit 305 controls the current detector302, the voltage detector 303, and the communication unit 304 and cancalculate the temperature of the battery pack 100 from the resistancevalue calculated using the second measurement method. The control unit305 integrates the charging current flowing through the battery cell100, which is detected by the current detector 302, thereby calculatingthe charge capacity of the battery cell 101.

In the first embodiment, the charging current value detected by thecurrent detector 302, the charging voltage value detected by the voltagedetector 303, the temperature of the battery pack 100 calculated by thecontrol unit 305, and the charge capacity of the battery cell 101calculated by the control unit 305 are called “charge stateinformation”. The control unit 305 compares the charge state informationwith the battery state information sent from the battery microcomputer102. If the difference between the charge state information and thebattery state information exceeds a preset value, the control unit 305determines that the battery pack 100 attached to the charger 200 is notin a normal state and sends a charging stop signal to the chargingcontrol IC 203. The communication unit 304 communicates with thecommunication unit 106 in the battery pack 100 and receives the batterystate information.

FIG. 2 is a flowchart describing an operation of charging, with the useof the charger 200 that charges the battery pack 100 attached to thecharger 200.

In step S001, the charger microcomputer 301 determines whether thebattery pack 100 is attached to the charger 200. If it is determinedthat the battery pack 100 is attached to the charger 200 (YES in stepS001), the flowchart proceeds from step S001 to step S002. In step S002,the charger microcomputer 301 starts charging the battery pack 100. Instep S003, the voltage detector 303 detects the terminal voltage of thebattery pack 100 and determines whether the terminal voltage of thebattery pack 100 is a voltage value at which communication between thecharger microcomputer 301 and the battery microcomputer 102 can beperformed. If it is determined that the terminal voltage of the batterypack 100 is a voltage value at which communication can be performed (YESin step S003), the flowchart proceeds from step S003 to step S004.

In step S004, communication between the charger microcomputer 301 andthe battery microcomputer 102 is started. Specifically, the batterymicrocomputer 102 sends battery state information output from thecontrol unit 107 via the communication unit 106, and the chargermicrocomputer 301 receives the battery state information via thecommunication unit 304. In step S005, it is determined whether thecharging of the battery pack 100 attached to the charger 200 iscompleted. Whether the charging is completed is determined depending onwhether a preset completion condition is satisfied. If the completioncondition is satisfied (YES in step S005), the flowchart proceeds fromstep S005 to step S006. In step S006, the charger microcomputer 301controls the charging control IC 203 to stop charging. If the completioncondition is not satisfied, the charging is continued.

FIG. 3 is a flowchart describing a measurement value checking operationthat is repeatedly executed at 30-second intervals (predetermined timeintervals) between steps S004 and S005 of the charging operation shownin FIG. 2. The measurement value checking operation is an operation ofcomparing, with the use of the control unit 305 in the chargermicrocomputer 301, the charge state information with the battery stateinformation sent from the battery microcomputer 102 and determiningwhether the battery pack 100 is not in the normal state.

In step S101, the control unit 305 determines a comparison item. If thecomparison item is determined as a “voltage value”, the charging voltagevalue detected by the voltage detector 303 is compared with the chargingvoltage value detected by the voltage detector 105.

If the comparison item is determined as a “current value”, the chargecurrent value detected by the current detector 302 is compared with thecharge current value detected by the current detector 104. If thecomparison item is determined as a “temperature”, the temperature of thebattery pack 100 calculated by the control unit 305 is compared with thetemperature of the battery pack 100 calculated by the control unit 107.If the comparison item is determined as a “charge capacity”, the chargecapacity of the battery cell 101 calculated by the control unit 305 iscompared with the charge capacity of the battery cell 101 calculated bythe control unit 107. That is, comparison is performed between thecharge state information and the battery state information of the sametype as the comparison item.

In step S102, the control unit 305 sets a determination value α neededto determine whether the battery pack 100 is not in a normal state. Instep S103, the charger microcomputer 301 at least detects or calculatescharge state information corresponding to the comparison item determinedin step S101. In step S104, the charger microcomputer 301 communicateswith the battery microcomputer 102 and at least receives battery stateinformation corresponding to the comparison item determined in stepS101. In step S105, the control unit 305 compares the charge stateinformation detected or calculated in step S103 with the battery stateinformation of the battery pack 100, which is received in step S104, andcalculates the difference between the charge state information and thebattery state information.

In step S106, it is determined whether the difference calculated in stepS105 is less than or equal to the determination value α set in stepS102. If the difference calculated in step S105 is less than or equal tothe determination value α (YES in step S106), the flowchart proceedsfrom step S106 to step S107. In step S107, it is determined that thebattery pack 100 is in the normal state, and the flowchart proceeds fromstep s107 to step S108. In step S108, the operation of charging thebattery pack 100 is continued. In contrast, if the difference calculatedin step S105 is not less than or equal to the determination value α (NOin step S106), the flowchart proceeds from step S106 to step S109. Instep S109, it is determined that the battery pack 100 is not in a normalstate, and the flowchart proceeds from step S109 to step S110. In stepS110, the charger microcomputer 301 controls the charging control IC 203to stop the operation of charging the battery pack 100. After theprocess of step S110, the measurement value checking operation shown inFIG. 3 and the charging operation shown in FIG. 2 are terminated.

As described above, according to the first embodiment, the charger 200can determine, using battery state information received from the batterypack 100 and charge state information detected or calculated by thecharger 200, whether the battery pack 100 is not in a normal state.

If the charger 200 determines that the battery pack 100 is not in anormal state, the charger 200 can stop the operation of charging thebattery pack 100. Therefore, the operation of charging the battery pack100 is safely controlled by the charger 200.

Second Embodiment

FIG. 4 is a flowchart describing a measurement value checking operationof the charger 200 according to a second embodiment of the presentinvention. In the second embodiment, there are described different partsof the first embodiment.

Referring to FIG. 4, steps S101 to S110 are the same as those of themeasurement value checking operation according to the first embodimentdescribed using FIG. 3. These steps are given the same referencenumerals as those in FIG. 3, and descriptions are not repeated.

In step S201, the control unit 305 corrects the charge state informationdetected or calculated in step S103. In step S202, the control unit 305corrects the battery state information received in step S104. Forexample, if the comparison item is a “voltage value”, voltage drops atthe measurement points are corrected in steps S201 and S202.

That is, there are factors causing voltage drops at the measurementpoints at which the charging voltage value is detected by the voltagedetector 303 and at which the charging voltage value is detected by thevoltage detector 105. Specifically, the charger microcomputer 301 andthe battery microcomputer 102 correct, for example, a voltage drop dueto the current control device 204 and the current detecting device 205,and a voltage drop due to a contact resistance or line impedance betweenthe terminal of the charger 200 and the terminal of the battery pack100.

As described above, according to the second embodiment, the charger 200can more accurately determine, using battery state information receivedfrom the battery pack 100 and charge state information detected orcalculated by the charger 200, whether the battery pack 100 is not in anormal state.

If the charger 200 determines that the battery pack 100 is not in anormal state, the charger 200 can stop the operation of charging thebattery pack 100. Therefore, the operation of charging the battery pack100 is safely controlled by the charger 200.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No.2007-336845 filed Dec. 27, 2007, which is hereby incorporated byreference herein in its entirety.

1. A charger that charges a battery unit including a secondary battery,comprising: a receiving unit that receives, from the battery unit,battery state information indicating a state of the battery unit, if thesecondary battery is being charged; a detection unit that detects chargestate information indicating a state of the battery unit, if thesecondary battery is being charged; a determination unit thatdetermines, using the battery state information and the charge stateinformation, whether the battery unit is in a normal state; and acontrol unit that controls charging of the secondary battery in thebattery unit depending on whether the battery unit is in the normalstate.
 2. The charger according to claim 1, wherein the determinationunit determines, using a difference between the battery stateinformation and the charge state information, whether the battery unitis in the normal state.
 3. The charger according to claim 2, wherein,the determination unit determines that the battery unit is in the normalstate, if the difference is less than or equal to the predeterminevalue.
 4. The charger according to claim 1, wherein the battery stateinformation and the charge state information indicate at least one of acharging voltage value, a charging current value, a temperature, and acharge capacity of the battery unit.
 5. The charger according to claim1, further comprising a correction unit that corrects the charge stateinformation, wherein the determination unit determines, using thebattery state information and the charge state information corrected bythe correction unit, whether the battery unit is in the normal state. 6.The charger according to claim 5, wherein the battery state informationand the charge state information indicate a charging voltage value ofthe battery unit.
 7. The charger according to claim 1, wherein thecontrol unit controls to stop charging the secondary battery if thedetermination unit determines that the battery unit is not in a normalstate.
 8. A charging system comprising: a battery unit including asecondary battery; and a charger that charges the secondary battery,wherein the battery unit includes: a first detection unit that detectsbattery state information indicating a state of the battery unit, if thesecondary battery is being charged; and a sending unit that sends thebattery state information to the charger, and wherein the chargerincludes: a second detection unit that detects charge state informationindicating a state of the battery unit, if the secondary battery isbeing charged; a receiving unit that receives the battery stateinformation from the battery unit, if the secondary battery is beingcharged; a determination unit that determines, using the battery stateinformation receiving unit and the charge state information detected,whether the battery unit is in a normal state; and a control unit thatcontrols charging of the secondary battery in the battery unit dependingon whether the battery unit is in the normal state.
 9. The chargingsystem according to claim 8, wherein the determination unit determines,using a difference between the battery state information and the chargestate information, whether the battery unit is in the normal state. 10.The charging system according to claim 9, wherein the determination unitdetermines that the battery unit is in the normal state, if thedifference is less than or equal to a predetermine value.
 11. Thecharging system according to claim 8, wherein the battery stateinformation and the charge state information indicate at least one of acharging voltage value, a charging current value, a temperature, and acharge capacity of the battery unit.
 12. The charging system accordingto claim 8, wherein the charger further includes a correction unit thatcorrects the charge state information, wherein the determination unitdetermines, using the battery state information and the charge stateinformation corrected by the correction unit, whether the battery unitis in the normal state.
 13. The charging system according to claim 12,wherein the battery state information and the charge state informationindicate a charging voltage value of the battery unit.
 14. The chargingsystem according to claim 8, wherein the control unit controls to stopcharging the secondary battery if the determination unit determines thatthe battery unit is not in a normal state.